As Bonzo mentioned this doesn't seem to be a Group problem as Canvas also has some long times. UIComponent is lighter than both Canvas and Group and it still has a couple entries longer than a few ms. Notice that using Sprite or GraphicElement is much faster. GraphicElement is very lightweight, are you able to use it instead of a Group? 100,000 Groups seems like a lot, can you explain your use case, maybe there is a way to use virtual layout to minimize the number needed at any one time?

I think the container.push() call might be causing a lot of the delay, if you use: